The compounds of formula I are described as interphenylene 9-thia-11-oxo-12-azaprostanoic acids and derivatives as a means of describing the structural relationship to prostanoic acid, which has the carbon skeleton of the natural prostaglandins as shown in the following formula: ##STR16##
The prostaglandins constitute a class of highly functionalized C.sub.20 fatty acids. They have been shown to occur extensively in low concentrations in mammalian tissues where they are both rapidly anabolized and catabolized and to exhibit a broad spectrum of pharmacological activities including prominent roles in (a) functional hyperemia, (b) the inflammatory response, (c) the central nervous system, (d) transport of water and electrolytes, and (e) regulation of cyclic AMP. Further details concerning the prostaglandins can be found in recent reviews of their chemistry [J. E. Pike, FORTSCHR. CHEM ORG. NATURST., 28, 313 (1970) and G. F. Bundy, A. REP. IN MED. CHEM., 7, 157 (1972)]; biochemistry [J. W. Hinman, A. REV. BIOCHEM., 41, 161 (1972)]; pharmacology [J. R. Weeks, A. REV. PHARM., 12, 317 (1972)]; physiological significance [E. W. Horton, PHYSIOL. REV. 49, 122 (1969)]; and general clinical application [J. E. Hinman, POSTGRAD MED. J. 46, 562 (1970)].
The potential application of natural prostaglandins as medicinally useful therapeutic agents in various mammalian disease states is obvious but suffers from three formidable major disadvantages, namely, (a) prostaglandins are known to be rapidly metabolized in vivo in various mammalian tissues to a variety of metabolites which are devoid of the desired original biological activities, (b) the natural prostaglandins are inherently devoid of biological specificity which is requisite for a successful drug (since this property is responsible for intolerable side effects), and (c) although limited quantities of prostaglandins are presently produced by both chemical and biochemical processes, their production cost is extremely high; and consequently, the availability is quite restricted.
Our interest has, therefore, been to synthesize novel compounds with the following unique advantages: (a) simplicity of synthesis leading to low cost of production; (b) specificity of biological activity; and (c) metabolic stability so that activity can be obtained on oral as well as parenteral administration.
In accordance with the present invention, there is provided a novel group of aza-prostanoic acids of formula I hereinabove. Surprisingly, the compounds of the present invention have a specific range of biological activities and do not possess the broad spectrum of biological activity possessed by the natural prostaglandins and their analogs. The compounds of the present invention, for example, are completely inactive in the mouse ovary prostaglandin assay which measures increases in cellular cyclic adenosine monophosphate levels ordinarily caused by prostaglandins and related compounds.
The compounds of the present invention, in addition, are highly potent, orally effective renal vasodilators having a sustained biological action but with reduced side effects and, therefore, are useful for the treatment of patients with renal impairment. Included in this group are patients with hypertension, renal failure, congestive heart failure, glomerulonephritis, uremia, and chronic renal insufficiency. The compounds of this invention by virtue of their renal vasodilatory activity improve renal function both when used alone or in conjunction with other renal agents. An example of a compound with high renal vasodilatory activity is 4-{3-[3-[2-(1-hydroxycyclohexyl)ethyl]-4-oxo-2-thiazolidinyl]propyl}benzoi c acid.
The compounds of the present invention are also orally effective antihypertensive agents and as such are useful in reducing blood pressure in individuals affected by this problem. The compounds of the present invention are surprisingly potent in their antihypertensive effect when compared with structurally related compounds.
The compounds of this invention have adjunctive properties which give them added utility for the treatment of renal disease. Such properties include antiasthmatic (bronchorelaxant), cardiotonic, and immunoregulant activities.
A further area of usefulness of the compounds of this invention is in the prevention of organ transplant rejection.
The compounds of this invention can be administered intravenously, subcutaneously, intramuscularly, orally, rectally, or by aerosolization in the form of sterile implants for long action. They can be formulated in any of a number of pharmaceutical compositions and nontoxic carriers to this end.
The pharmaceutical compositions can be sterile, injectable suspensions or solutions, or solid, orally administrable, pharmaceutically acceptable tablets or capsules; the compositions can also be intended for sublingual administration, or for suppository use. It is especially advantageous to formulate compositions in dosage unit forms for ease and economy of administration and uniformity of dosage. "Dosage unit form" as a term used herein refers to physically discrete units suitable as unitary dosages for animal and human subjects, each unit containing a predetermined quantity of active material calculated to produce the desired biological effect in association with the required pharmaceutical means.
Illustratively, a sterile injectable composition can be in the form of aqueous or oleagenous suspensions or solutions.
The sterile, injectable composition can be aqueous or oleagenous suspension or solution. Suspensions can be formulated according to the known art using suitable dispersing and wetting agents and suspending agents. Solutions are similarly prepared from the salt form of the compound. For the laboratory animals, we prefer to use incomplete Freund's adjuvant or sterile saline (9%) as carrier. For human parenteral use, such as intramuscularly, intravenously, or by regional perfusion, the diluent can be a sterile aqueous vehicle containing a preservative, for example, methylparaben, propylparaben, phenol, and chlorobutanol. The aqueous vehicle can also contain sodium chloride, preferably in an amount to be isotonic, as well as a suspending agent, for example, gum arabic, polyvinyl pyrrolidone, methyl cellulose, acetylated monoglyceride (available commercially as Myvacet from Distillation Products Industry, a division of Eastman Kodak Company), monomethyl glyceride, dimethyl glyceride, or a moderately high molecular weight polysorbitan (commercially available under the tradenames Tween or Span from Atlas Powder Company, Wilmington, Delaware). Other materials employed in the preparation of chemotherapeutic compositions containing the compound may include glutathione, 1,2-propanediol, glycerol, and glucose. In addition, the pH of the composition is adjusted by use of an aqueous solution such as tris(hydroxymethyl)aminomethane (tris buffer).
Oily pharmaceutical carriers can also be used, since they dissolve the compound and permit high doses. Many oily carriers are commonly employed in pharmaceutical use, such as, for example, mineral oil, lard, cottonseed oil, peanut oil, sesame oil, or the like.
It is preferred to prepare the compositions, whether aqueous or oils, in a concentration in the range of from 2-50 mg./ml. Lower concentrations require needless quantities of liquid. Higher concentrations than 50 mg./ml. are difficult to maintain and are preferably avoided.
Oral administration forms of the drug can also be prepared for laboratory animals or human patients provided that they are encapsulated for delivery in the gut. The drug is subject to enzymatic breakdown in the acid environment of the stomach. The same dosage levels can be used as for injectable forms; however, even higher levels can be used to compensate for biodegradation in the transport. Generally, a solid unit dosage form can be prepared containing from 0.05 mg. to 10 mg. active ingredient and preferably from 0.1 mg. to 1 mg. of active ingredient.
Whatever the mode of administration, doses in the range of about 0.05 to 10 milligrams per kilogram of body weight, preferably 0.1 to 1 mg., administered one to four times per day are used, the exact dose depending on the age, weight, and condition of the patient, and the frequency and route of administration.
The low cost and ready accessibility of the compounds of this invention make them particularly promising for applications in veterinary medicine in which field their utilities are comparable to those in human medicine.